1. Field of the Invention
The present invention relates to a recording control method, recording control device and inspection method of an optical recording medium, and more particularly to a recording control method, recording control device and inspection method for an optical recording medium which employs an organic dye which is suitable for high-speed recording of the optical recording medium.
2. Description of the Related Art
Optical recording media (optical discs) are known on which information can be recorded in write-once modes and the like with laser light. Among these optical discs, optical discs with greater recording capacity than flexible discs are known (“CD-R”). Recording of information thereon is performed by irradiating a CD-R with laser light in the near infrared region (for example, a wavelength in the vicinity of 780 nm). The recording of information is realized by a change in optical characteristics due to an irradiated region of a recording layer absorbing the laser light, experiencing a localized temperature rise, and physically or chemically changing (for example, pits being created).
In recent years, with the advance of digitalization throughout society, volumes of information to be distributed have been generally increasing. In response to demands for optical recording media with greater capacities, larger capacity optical discs (write-once digital versatile discs, known as DVD-R, DVD-RW, etc.) are now being marketed. These DVD-Rs and the like are formed by providing a recording layer formed with a dye, a light reflection layer and, as necessary, a protective layer in this order on a transparent disc-form substrate. In this substrate, a guide groove for tracking of irradiated laser light (a pre-groove) is formed at least half as narrowly as in a CD-R (i.e., at 0.74 to 0.8 μm). For recording and playback of information on DVD-Rs, laser light of wavelengths shorter than for CD-Rs (for example, wavelengths of 630 to 680 nm) is irradiated, and thus higher density recording than in CD-Rs is possible.
Anyway, at a CD-R/W, DVD-R/RW or DVD+R/RW, a PCA (power calibration area) region for performing calibration of recording laser power is provided at a predetermined position at an innermost periphery or an outermost periphery of the disc. At this PCA region, block units are defined. Using these plural block units, recording formats and recording signals of a particular recording apparatus from a particular company are written and played back, and an optimal recording power for carrying out recording is determined.
For example, describing a DVD-R as an example, hitherto, a particular pattern (for example, a pattern in which 3T and 14T marks are repeated, or the like) has been test-written with recording power being changed in a stepwise manner. Actual recording has been performed with a recording power at which a target β value, which was recorded beforehand at substrate land pre-pits (LPPs) of the DVD-R, is obtained.
Now, a technology, described in Japanese Patent Application Laid-Open (JP-A) No. 6-236553, has been proposed in which, just before shipment of a disc or just, before recording, an evaluation pattern is recorded at an optical recording medium. The evaluation pattern, in which data ones (“1”) and zeros (“0”) are recording data of a modulated binary signal, includes at least a thermal/optical interference region, which is a range in which, through a recording and playback process, a particular data one is affected by surrounding data ones or zeros. Positions of data ones or zeros relative to reference positions are found. With a binarized signal of playback data obtained from this evaluation pattern, positional offsets between the positions of data ones or zeros relative to the reference positions and positions of data ones or zeros of the playback data corresponding thereto are detected. These positional offsets are analyzed, and thus variations of the binary signal that have occurred in the recording and playback process are detected.
Further, a technology, described in JP-A No. 2002-237041, has been proposed in which a level of a portion of a playback signal corresponding to a repeated pattern y, played back from a magneto-optical disc on which information has been recorded by a light beam, and a level of a portion of the playback signal corresponding to a solitary mark pattern x are detected. Recording conditions are determined by comparison of these levels. Specifically, a high level (or low level) of the playback signal corresponding to the repeated pattern y is compared with a high level (or low level) of a portion of the playback signal that corresponds to the solitary mark pattern x, and a recording power is set such that the levels are the same. When the recording power is determined in this manner, thermal interference can be made equal between recording marks corresponding to different mark patterns.
However, in high-speed recording of optical recording media, the effects of thermal interference become even more significant. Specifically, a power margin at a high power side (an asymmetry increasing side) is reduced, and a small increase in recording power leads to a sharp increase in jitter and errors. Therefore, recording with higher recording power is not desirable in regard to the medium. However, in regard to the drive, in order to preserve margins during playback, it is desirable to record with a recording power at which asymmetry is increased (i.e., recording power is increased) as much as is feasible.
As described above, given the circumstances in regard to the medium and in regard to the drive, a number of deficiencies in the related art still exist. Thus, a technique which, when high-speed recording is to be performed, specifies a recording power which is as high as possible and ensures that satisfactory recording can actually be carried out in practice is required. The present invention seeks to correct these deficiencies and has been devised in consideration of the circumstances described above, and provides an optical recording medium recording control method, recording control device and inspection method which are capable of assigning a recording power as high as possible in a range with which satisfactory recording is possible.
Now, the technology described in JP-A No. 6-236553 provides recommendations as far as detection of variations of playback signals, but does not go on to discuss how to assign recording powers in practice.
Meanwhile, the technology described in JP-A No. 2002-237041 compares the high level (or low level) of the playback signal corresponding to the repeating pattern with the high level (or low level) of the portion of the playback signal corresponding to the solitary mark pattern and assigns a recording power such that these levels are equal. However, there is no consideration of recording with recording powers that are any higher. That is, there are no suggestions pertaining to a method of determining recording power in the context of high-speed recording.